david23 wrote:no they stay folded because of the inter and intra molculecular forces.

Don't say. So, if you change some glycine, which is inside of the protein into fenylalanine, than you will still get working 3D protein? Or if will you change some Ala in alpha-helix into proline, than you will still get protein with working 3D structure? Only this minor change may cause total disruption of the structure, because after that you won't be able to get the other interactions either.